I returned from Orlando depressed. I was there reporting a few days after a man had opened fire in a crowded nightclub with a semi-automatic weapon, killing 49 and wounding dozens of others. Mass shootings have been a common news item in the United States over the last few years, but this one seemed different, both in its scale and in the response (or lack thereof) that followed.

After Columbine (two high school seniors shot and killed 12 students and one teacher), Sandy Hook (one man shot and killed 20 six- and seven-year-olds and six adults), Fort Hood (an Army major shot and killed 13 people and injured 30 more), the Navy Yard in Washington, D.C. (a man shot and killed 12 at a naval base), Aurora (a man shot and killed 12 and injured 70 in a movie theater), and Charleston (a white supremacist shot and killed nine black churchgoers), there was at least debate about what to do. Background checks? End the sale of assault rifles? Create an interstate tracking system?

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In the four years immediately following the conclusion of Lott’s 1997 study, 14 more jurisdictions passed concealed-carry laws. Ian Ayres, a lawyer and economist at Yale Law School, and Stanford Law School professor John Donohue, both of whom have published extensively on gun control, jointly wrote a 106-page takedown of Lott’s work in 2002. They decided to add those 14 jurisdictions to Lott’s models, and found that, in every jurisdiction, all categories of crime increased after concealed-carry laws were passed.

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“What I dislike is he says all these things that are clearly wrong, and his science is not very good at all,” Hemenway says. John Donohue says Lott obfuscates with bad data, and won’t admit when he’s wrong. “Lott’s work was mainstreamed very quickly because it did appeal to a powerful economic interest, and political interests, and so the work got more prominence more rapidly than it probably deserved.”